Process for the optical brightening of polyacrylonitrile fibers



United States Patent 3,005,779 PROCESS FOR THE OPTICAL BRIGHTENING FPOLYACRYLONITRILE FIBERS Franz Ackermann, Binningen, and Adolf EmilSiegrist, Basel, Switzerland, assignors to Ciba Limited, Basel,Switzerland No Drawing. Filed Aug. 3, 1959, Ser. No. 831,067 Claimspriority, application Switzerland Feb. 15, 1955 17 Claims. (Cl.252-3012) 1 This is a continuation-in-part of our copending patentapplication Serial No. 563,457, now US. Patent No. 2,977,319 filedFebruary 6, 1956. i

The invention relates to a process for the optical brightening ofpolyacrylonitrile fibers which comprises treating said fibers with acompound of the formula wherein X and X each represents a memberselected from the group consisting of a hydrogen atom, a chlorine atomand a lower alkyl group having at most 3 carbon atoms and Y and Y each.represents a member selected (2) N p N\ v CCH=CHC/ N N l i The presentinvention relates further to a composition of matter substantiallyconsisting of polyacrylonitrile fibers having incorporated a smallquantity of an optical brightening agent of the general Formula 1 or ofthe Formula 2.

The 2:S-di-[benzimidazyl-(Z)]-furans of the general Formula 1 can bemade by heating an ortho-diamine of the benzene series, of which oneamino group is primary and the other amino group is at most secondaryand which may contain a chlorine atom or an alkyl group of low molecularweight in the benzene nucleus, with furan- 2:5-dicarboxylic acid, and,when the ortho-diamine used as starting material contains two primaryamino groups, if desired, treating the resulting 2:5-di[benzimidazyl-(2') ]-furan with an alkylating hydroxyalkylating, alkenylating oraralkylating agent.

The reaction is advantageously carried out at a temperature of at least190 C. However, the dibenzimidazylfurans can also be obtained, asdescribed for the known compound in US. Patent No. 2,463,264 patentedMarch 1, 1949 by Charles Greanacher et a1., by reacting the componentstogether at a temperature below 190 C., for example, at about 150 C.,but substantially lower yields are obtained.

In general, the two starting materials are advantageously used for thereaction in at least approximately the theoretical proportions, that isto say, that for every molecular proportion of furan dicarboxylic acidthere are used 2 molecular proportions or an amount at most a mixingthem together in the solid state.

few percent more or less than 2 molecular proportions;

of the. diamine. While the reaction can be carried out in a suitablehigh boiling solvent, this usually leads to less satisfactory resultsthan'when the reaction mixture consists solely of the two startingmaterials and, if desired, a small proportion of boric acid.

The i presence of boric acid increases the yield quite considerably. Theproportion of boric acid is advantageously about 0.5% to 5% calculatedon the total weight of the reaction mixture.

Furthermore, it is of advantage to carry out the reaction in the absenceof oxygen (air), for example, in vacuo or advantageously in an inertgas, such as nitrogen.

The procedure may, for example, consist in heating together the twostarting materials at about 140 to 150 C.

in the presence or absence of boric acid, if desired, after Theresulting melt is then gradually raised to about 200 C. While thusincreasing the temperature, the elimination of water sets in. The periodduring which the temperature is raised from 140 C. to about 200 C.should not be too long,

- as otherwise there is a risk of the melt thickening or'even 5 organicsolvent, precipitating the imidazole in'the form of a salt, which isusually sparingly soluble in water, by adding a dilute mineral acid, forexample, sulfuric acid or hydrochloric acid, and then separating thesalt from the aqueous solution;' From the salt the base can be liberatedwith the aid of an alkali, such as an alkali metal carbonate or ammonia.

Instead of using as starting materials for the manufacture of the furancompounds substituted at the imidazole nitrogen atoms, for example,those of Formula 1,

' diamines which contain a secondary amino group, the

substituents in question (Y and/or Y see above) may be subsequentlyintroduced into 2:5-di- [benzimidazyl- (2')]-furans unsubstituted at theimidazole' nitrogen atoms, and one or both of the hydrogen atoms boundto nitrogen may be thus exchanged for substituents.

= The material to be improved by the use of the present process canexist in any stage of processing, it being obviously advantageous totreat it in the described manner at a stage when all other treatmentshave been completed 1 which would have-the eifect of removing again theagent used according to the invention or would have an un-- favorableeffect upon it. The agents used can for exam-' ple be added to thematerials to be improved either before or during the shaping thereof.Thus they can be dissolved or finely distributed in a spinning massbefore the spinning thereof.

Fibers can be used in the application of the present process whicheither consist of polyacrylonitrile alone orof fiber mixtures consistingto a substantial extent of polyac'rylonitrile fibers, or of fibersconsisting of copolymers containing other compounds in addition topolyacrylonitn'le. r

" Especially valuable results are generally obtained with those2,5-di-[benzimidazyl-(2)]-furans of the general Formula 1 whose benzeneradicals are substituted by low present process which can exist asstaple fibers or mono- Patented Oct. 24, 19.61-

dissolved or suspended. If desireddispersing agents can.

be added in the'treatment for example soaps, polyglycol ethers of fattyalcohols or fatty amines, ,cellulose 'sulfite waste liquor orcondensation products with formaldehyde of naphthalene sulfonic acidswhich may be alkylated.

It is of particular advantage, especially when the treatment of thefibers is exclusively for the purpose of proving the optical properties,to work in weakly alkaline o i b h p efe a y weakly ac ba hs, f xampcontaining acetic acid or formic acid. It is likewise of advantage ifthe treatment takes place at elevated temperature, for example at theboiling temperature of the bath or in the neighbourhood thereof (about90 ;C It is surprising that the compounds of the composition set forthabove possess a good affinity for the fibers and can be fixed thereon ina similar manner to dyestuifs. In this connection it may be remarkedthat in the case of these synthetic fibers many optical improving and rin n a en w h a 9 oo ap l s b li v o other fiber materials, cannot be.used for the reason that in this ease they cannot be fixed on the fiberor do not give rise to the desired efiect. The fastness to light of thematerials treated according to the present process is also good, theefiect persisting even after long exposure to ht- The quantity of theimproving agent to be used, calr culated on the material to be treated,can vary within wide limits. Even with very small quantities, in somecases for example, of 0.01 percent, a distinct and permanent eifect canbe attained. Althoughquantities of more than about 3 percent are ingeneral not disadvantageous, they offer no advantages compared with thenormal quantities.

As indicated above, the present process can advantageously be combinedwitth other processing methods. Thus the compounds to be used accordingto the present invention can also be applied as follows:

(a) In admixture with dyestuffs or as additions to .dyebaths ,orprinting, discharge or reserve pastes. Further also for theafter-treatment of dyeings, prints or discharge prints, especially inthe soaping process. Thus, for ex,- ample, polyacrylonitrile fibers canbe simultaneously dyed and improved as regards optical properties in anacid medium and are dyed in the same bath with azo dyestuifs which arefree from sulfonic acid groups and w ic c ai as sa ups m no g oup saform with acids in an acid medium salts which at the most are partiallyhydrolyzable, these dyestuffs being fixed on the fiber in the formof-their salts.

(b) In ad i tu e with chem a b each n a nt o as additions to bleachingbaths.

c m ti n w a h n n s; Th s in agents and brightening agents can beseparately added to the washing baths to be used. It is alsoadvantageous to use a i g age w c on r h nin a ents dmixed therewith. As washing agents are suitable for amp s ap (s d s t .1" hi he fatty asdfl a t of sulfonate washing agents, as for example, ofsulfonatedbenzimidazoles substituted on the Z-carbon atom by higher alkylradicals, also salts of monocarboxylic acid esters of 4-sulfophthalicacid with higher fatty alcohols or salts .of fatty alcohol sulfonates,alhylaryl sulfonic acids or condensation products of higher fatty acidswith aliphatic hydroxyor amino-sulfonic acids. Non-ionic washing agentscan also be used, for example polyglycol ethers which are derived fromethylene oxide and higher fatty alcohols, alkyl phenols or fatty amines.

The washing agents of the above specified type can also contain thecustomary washing agent additions, such as alkali metal carbonates,phosphates, pyrophosphates, polyphosphates, metaphosphates, silicates,perborates or psr ar nst s ens a he b shteains sls a ask treatedmaterial.

patible with such additions. It is also possible to prepare washingagents which consist solely or for the most part of inorganic compoundsof cleansing effect and the brightening agents. The production of themixtures of the washing agents and optical brightening agents takesplace in a simple manner by mixing and/or grinding of the componentstogether. In this case it may be of advantage to use or the othercomponent in the dissolved or molten condition for the purpose offacilitating distribution.

In general a small addition of the optical improving agents to thewashing agents suffices. There are .concerned, for example, quantitiesof 0.1 to 5 percent calculated on the washing agent. Also smallerquantities, for example, 0.01 percent or even less can be added. Alsomixtures with other known brightening agents can be usedf The washingagents are used asin the customary washing processes. In this mannermaterials to be cleansed canbe simultaneously washed and brightened.Whenthe present process is combined with other treatment or improvementmethods, for example those set forth above under (a) to (c), thecombined treatment advantageously takes place with the aid of suitablecon stituted preparation. These stable preparations are characterized bya content of imidazoles of the type specified above, and also furthertextile treating agents, for example dyestuffs, chemical bleachingagents, finishing agents or especially washing agents.

The following examples illustrate the invention, the p t a d Pers t s sng b Weight unl s qth w s stated.

E a p 1 Polyacrylonitrile fabric, for example "-Orlon is treated at abath ratio 1:50 with 0.01 percent of 2:5-di- [benzimidazyl-(2')]-furanfor 30 minutes at about90 C. in a 'bath containing per liter 1 gram ofpercent formic acid. The material is then rinsed and dried. Theresulting material \possessesa higher white content than the un- Similareifects are obtained when instead of 2:5-di-[benzimidazyl (2')] furanthe diimidazoles of the following formulae are used:

(3) /N HC CH N\ \s H/ Y\ O N N lHs (4) /N HC CH or when .the:B-diibenzimidaayl-(Z')Lethylene is used. The 2:;5-di-[benzimidazyl-(2')] furan can be prepared in the following manner:

108 parts of 1:2-diaminobenzene, 78 parts of pure furan- 2 :5.-dicarboxylic acid and 3 parts of boric acid are t r d or 70 m nu es t2- 6" in a we: O n ssnh tem e atu is hen a ed w thin 30 m was t 0 hichca s l w el mina ion we. The mixture is then stirred for 1 ,hO r at 210to 220 C.

150 parts of glycol are then added, whereupon the temperature drops to150 C. Immediately afterwards, 1000 parts of 2 N-hydrochloric acid areadded, and the mixture is stirred for /2 hour at C., allowed to cool,suctionfiltered, and the filter cake is washed three times with 300parts of water and then stirred for /z hour at 70 C. in 0 P rts of w t rqqnta fms 0 Pa t of mn s a Q 30% strength. The yellow condensationproduct is allowed to cool to room temperature, suction-filtered andwashed three times with 300 parts of water. After drying, about 105parts of the condensation product of the formula I H -o (3-0 melting at292.5-294 C. are obtained.

The water of crystallization can be removed by heating the product for30 minutes at 230 C. under a pressure of 0.01 mm. Hg. The dehydratedproduct yields the following data:

Calculated: C, 71.99%;H, 4.03%;N, 18.66%. Found: C, 71.79%; H, 4.18%; N,18.76%.

When the process described above is performed without the addition ofboricacid, the yield obtained is by a few percent lower.

The compound of Formula 3 can be prepared in the following manner:

15 parts of 2:5-di-[benzimidazyl-(2')]-furan are dissolved in 80 partsof ethanol of 90% strength containing 8 parts of sodium hydroxide. Asolution of 12.5 parts of dimethyl sulfate in 10 parts of'ethanol isthen stirred in at 75 C. dropwise in the course of 2 hours. Thetemperature of 75 C. is maintained for another hour, the solution ispoured into 1000 parts of Water, the precipitate is suctioned off anddried and yields about 14 parts of the compound of the Formula 3.

After having been recrystallized three times from aque ous ethanol, theproduct melts at 146-147 C. and gives the following analytical data:

C ,,H ON Calculated-C, 69.35%; Found-C, 69.24%; H, 4.95%.

The compound of the Formula 4 can be prepared in the following manner:

15.2 parts of 2:5-di-[benzimidazyl-(2')]-furan are dissolved in 100parts of 90% ethyl alcohol containing 6 parts of caustic soda. 8.2 partsof benzyl chloride are added with stirring in the course of 2 hours at atemperature of 75 C. The mixture is stirred for one hour, then pouredonto water and the crystalline product is suctionfiltered. The yield is18.8 parts.

After recrystallization from aqueous ethanol the product melts withdecomposition at about 250 C.

The mfl-di-[benzimidazyl-(Z)J-ethylene can be prepared in the followingmanner:

660 parts of o-phenylene diamine are heated with 116 parts of fumaricacid within 3 to 5 hours from 120 to 160 C. with the exclusionof air. Assoon as the elimination of water subsides, the temperature is raised toabout 190 C. and maintained for a short time until water no longerescapes. The whole is allowed to cool and the o-phenylene diamine inexcess removed by extraction with alcohol, benzene or another solvent.The residue is dissolved in hot dilute hydrochloric acid and thecondensation product precipitated from the solution by means of analkaline agent, e.g. with ammonia, filtered and washed neutral withWater.

Example 2 Polyacrylonitrile fabric (Orlon) is treated at a bath ratio1:40 with 0.03 percent, of 2:5-di- [benzimidazyl- (2')]-furan for 1 hourat about 95 C. in a bath containing per liter 5 g. of 85 percent formicacid and 5 g. of an addition product from about 30 mols of ethyleneoxide to a mixture of saturated fatty alcohols the majority of which has18 carbon atoms. The material is then rinsed and dried. The resultingmaterial possesses a higher white content than the untreated material.

Similar eiiects are obtained when instead of 2:5-di- 6[benzimidazyl-(2') J-fur-an a dimidazole of the Formula 2, 3 or 4 isused.

Example 3 I Polyacrylonitrile fabric, for example Orlon is treated at abath ratio 1:40 with 0.03% of the compound of the formula in a bathcontaining per liter 1 gram of formic acid, 2 grams of sodium chloriteand 2 grams of sodium nitrate. The material is then rinsed and dried.The resulting material possesses a higher white content than theuntreated material.

Similar effects are obtained, when instead of the compound (6) thefollowing eompound is used:

(7) N HO OH N afa/ t \6/ N N JaHs aHs The compound of Formula 6 can beprepared in the following manner:

10' parts of 2:5-di[benzimidazyl-(2')]-fi1ran are dissolved in 70 partsof ethanol of strength containing 8 parts of sodium hydroxide. Asolution of 6 parts of l-chloro-Z:3-di-hydroxypropane in 10 parts ofethanol is then stirred in dropwise at 75 C. in the course of 2 hours.The temperature of 75 C. is maintained for another hour, and thesolution is then poured into 500 parts of water, and the precipitate issuctioned off and dried,. to yield about 12 parts of the condensationproduct'of theFormuila 6. t

After having been recrystallized three times from aqueous ethanol, theproduct melts at 2905-291" C. and gives the following analytical data:

C H O N CalculatedC, 54.21%; H, 5.13%:N, 14.37%. FoundC, 64.58%; H,5.50%; N, 14.28%.

When 13 parts of l-bromo-propylene-(Z) .are used in-- stead of 6 partsof l-chloro-2:3-dihydroxypropane, the condensation with furandicarboxylic acid yields about 15 parts of the compound of the Formula7.

After having been recrystallized five from aqueous dimethyl formamide,the product-melts at 2985- 300 C. and yields the following analyticaldata:

C24H2403N4Z Calculated-C, H, 5.77%. FoundC, 69.22%; H, 5.60%.

Example 4 1500 cc. water 3 grams formic acid 85%.

3 grams sodium chlorite 0.1 gram of the above product,

then rinsed and dried. The material thus treated is whiter than amaterial which has been treated without the addition of the aboveproduct.

Similar elfects are obtained when instead of the 2:5-di

[benzi'rnidazyl-(Z') I-furan adimidazol'e of any of the followingformulae is used:

or when the azfl-di-[benzimidazyhfl'Methylene is used.

The compound of Formula 8 can be prepared in the following manner:

15 pants of 2z5-di-[benzimidazyl-(2')]-furan are dissolvedin SO-parts.of ethanol of 90% strength containing 8 parts of sodium hydroxide. Atthe boiling temperature of ethanol a solution of 6 parts. ofl-chloro-Z-hydroxyethanein. parts ofethanolv is added: drop-wise in thecourseof 1 hours. The solution; is stirred for /2 hour at: 70 C. andthen poured. into 500 parts of water. The

precipitated condensation product is. auctioned off and dried, to. yieldabout 16 parts; of the compound of the FOI'm1l1-h:8..

.After: having been. recrystallized three times from aqueousethanol;theproduct melts at 182l8.2.8 C.

C20H16O2N4I Ca1culated-C, H, N, 16.27%.. FoundC; 69;80%; H,.4.66%; N,16.49%.

W116Il16 partsof l-chloro-2ehydroxypropane are used instead of 6 partsof l-chloro-Z-hydroxyethane the condensati'on with thefuran-dicarboxylicacid yields. about 11 partsof" the compound of the Formula 9. Meltingpoint: 150 151. C..

The compoundtof; the'Formula. 10 can be prepared in thefollowingmannere- 10 parts of 4-chloro-l,Z-diamino-benZene, 5.6 parts of2:5'-furan.-dicarboxylic acid and0.2 part. ofv boric acid areheated=with stirringto2l0 C. in a currentof nitrogen for 90 minutes, themixture thickens, after 30 minutes and solidifies after 45 minutes.- Themelt iszdissolvedby. adding 20 parts of glycol, poured ontowater andisuction-filtered. The yield is about 9 parts.

After having been recrystallized three times from aqueous-ethanol,the.pro.duc t melts at 306; to 307.5 C.

Example 5 A soap is;pro ducedwhichcontains l percent-of 2:5-di-[benzimidazyl7(2: )7J-fUIaIl. Polyacrylonitrile fibers, for example*Qrlon, which have,-beenwashed with this soap, have a brighterappearance-than material which has only been washed with usual soap.

A similar efiect is achieved when instead of soap a synthetic washingmaterial is used or one of the following composition:

33.3% of soap 111098 of anhydrous'sodium carbonatel4.0% ofsodiumpyrophosphate 7.0% of sodium perborate 3 .0%- of-magnesium:silicate following formulae are used in the washing agent:

or the; mddi-[benzimidazyl-(Z')]ethylene is used. The compounds (10) and(11) can be prepared as follows:

24.4 partsof 4-methyl-l:Z-diaminobenzene, 15.6 parts offuran-ZzS-dicarboxylic acid and 0.5 part of boric. acid are: fused atl45'l50 Cr in a currentof nitrogen. The temperature is then raised to210-215" C. and: the melt isstirred on; for 2 hours at this temperature.40 parts of glycol arethen added to the melt, whereupon the temperaturedrops to 150:" C. The melt iscooled to 100 C. and: 200 parts'of 2-N-hydrochloric. acid are added. The mixture is then stirred for' /2 hourat C.,v cooled to room,

temperature, suction-filtered, and the. filter cakeiswashed three timeswith 60 parts of water. The filter residue is then stirred for /2w hourat 70 C. in 200! parts of water containing 15 parts of ammonia of 30%strength. The yellow condensation product isallowed to cool to roomtemperature, suction-filtered and the filter cake is washed three timeswith 60 parts of water.. After drying, about 24- parts of2:S-di-[6-methylrbenzimidazyl-(2f)] -furan are obtained. After havingbeen recrystallized twice from aqueous ethanol, the product is analyzedand. yieldsthe following data:

8; parts of 2:.5-di-[6'-rnethyl-benzimidazyl (2)' ]:-furau obtained.asdescribed. above are dissolvedin 50 parts of ethanol of 90% strengthcontaining 4 partsof sodium hydroxide.v A solution of 6 partsof.dimethyl. sulfate. in 10 parts of ethanol is thenaddeddropwise at 75C..-in, the course of 1 hour. Thesolution isstirred-for. another- /2hour at that temperature andthen poured into. 500' parts. of water,.andthe precipitate-issuctioned off andLdriecL-toyield about6 parts of thecompoundoftheFormula l0 and-2 parts of the Formula 11.

The product substituted at both nitrogen atoms melts at 236237.5 C.,whereas the product substituted atlonly one nitrogen atom melts at272272..5 C

Example. 6

Orion fabric is treated" for 1 hour at 90j-100 C;,in a bath whichcontains (calculated on the fabric) 1% of the dyestuff of the. formula3% 2:5-di- [benzimidazyl-(Z)]-furan and-3%. acetic acid of 86% strength.(Ratio of goods to.liquor-. 1440.).-

After being rinsed and dried the fabric-so treated has a. pure greenishblue shade.

Similar effects are obtained, when instead of 2:5'-di- [benzimidazyl=(2)]-furan .acompound Ofithe; Formula 8 or 9 is used, or when the compoundof the Formula 2'is used.

Fabric dyed in the same manner but without the addition of thedi-imidazole compounds is less pure in color and less greenish.

Example 7 of the compound of Formula 8 a compound of Formula 4 or 6 isused, or when the compound of the Formula 2 is used. 7

Example 8 30 parts of 2,5-di-[benzimidazyl-(2') J-furan are ground to afine, homogenous powder in a suitable mixing and grinding apparatus,with 60 parts of sodium bisulfate and 910 parts of a condensationproduct of "naphthalene sulfonic acid and formaldehyde.

Polyacrylonitrile fibers, for example Orlon, are treated for 30 minutesat 90-95 C. at abath ratio of 1:30 with 0.5 percent of this powder in abath which contains 1.5 grams per liter of 85 percent formic acid, thenrinsed and dried. The Orlon fiber thus treated has a higher whitecontent than the untreated material.

Similar brightening effects are obtained when a compound of the Formula2, 6 or 9 is used instead of 2:5-di- [benzimidazyl-(Z') -furan.

What is claimed is:

1. A process for the optical brightening of Polyacrylonitrile fiberswhich comprises applying to said fibers in aqueous medium from 0.01 to3.0 percent, calculatedjon the weight of said fibers, of a compound ofthe formula wherein X and X each represents a member selected from thegroup consisting of a hydrogen atom, a chlorine atom and a lower alkylgroup having at most 3 carbon atoms and Y and. Y each represents amember selected from the group consisting of a hydrogen atom, a loweralkyl group having at most 3 carbon atoms, a lower alkenyl group havingat most 3 carbon atoms, a lower mono-hydroxy alkyl group having at most3 carbon atoms, a lower di-hydroxy alkyl group having at most 3 carbonatoms and a benzyl radical.

2. A process for the optical brighteningof polyacrylonitrile fiberswhich comprises applying to said fibers in aqueous medium in a'finelydispersed state from 0.01 to 3.0 percent, calculated on the weight orsaid fibers, of

an optical brightening agent of the formula wherein X and X eachrepresents a. member selecteu from the group consisting of a hydrogenatom, a chlorine atom and a loweralkyl group having at most 3 carbonatoms and Y and Y each represents a member selected from the groupconsisting of a hydrogen atom, a lower alkyl group having at most 3carbon atoms, a lower alkenyl group having at most 3 carbon atoms, alower mono-hydroxy alkyl group having at most 3 carbon atoms, a lowerdi-hydroxy alkyl group having at most 3 carbon atoms and a benzylradical.

lab

10 3."A process for the optical brightening'of'polyacrylonitrile fiberswhich comprises applying to said fibers in aqueous medium in thepresence of a dispersing agent from'0'.01 to 3.0 percent, calculated onthe weight of said fibers, of an optical brightening agent of theformula 1v l i. wherein X and X each represent a member selected fromthe'groutp consistingof a hydrogen 'atom,a chlorine atom and a loweralkyl group having at most 3 carbon atoms and Y and Y each represents amember selected from the group consisting of a hydrogen atom, a loweralkyl group having at most 3 carbon atoms, a lower alkenyl group havingat most 3 carbon atoms, a lower mono-hydroxy alkyl group having at most3 carbon atoms, a lower di-hydroxy alkyl group having at most 3 carbonatoms and a benzyl radical. V I

4. A process for the optical brightening of polyacrylonitrile fiberswhich comprises applying to said fibers in aqueous medium in thepresence of a washing agent from 0.01 to 3.0 percent, calculated on theweight of said fibers, of an optical brightening agent of the formulawherein X and X each represents a member selected from the groupconsisting of a hydrogen atom, a chlorine atom and a lower alkyl grouphaving at most 3 carbon atoms and Y and Y each represents a memberselected from the group consisting of a hydrogen atom, a lower alkylgrouphaving at most 3 carbon atoms, a lower alkenyl group having at most3 carbon atoms, a lower'mono-hydroxy alkyl group having at most 3 carbonatoms, a lower di-hydroxy alkyl group having at most 3 carbon atoms and'a benzyl radical.

'5. A process for the optical brightening of polyacrylonitrile fiberswhich comprises applying to said fibers in aqueous medium from 0.01 to3.0 percent, calculated on the weight of said fibers, of the compound ofthe formula HCCH I oii i r-o CH N/ \O/ \N .1031,

\N I V I I 7. A process for the optical brightening of polyacrylonitrilefibers which comprises applying to said fibers in aqueous medium from0.01 to 3.0;percent, calculated on the weight of said fibers, of thecompound of the formula 11 8- .A pr es 9r the opt al bri htening o polvay ni i fi e s wh ch c mp se ppl in to a d zfibe s in. aque s m d um i om01 i031 perc nt; ca c l d o the w ig t f id fibe s. of t compo nd o he onml (EH: omen the weight of said fibers, of the compound of the formula10. A composition .of matter substantially consisting ,ofpolyacrylonitrile fibers having incorporated therein an op.- ticalbrightening agent in a proportion sufficient to brighten said fibers,said optical brightening agent being of the formula N N HC-GH at ."H/

I o N N i ll wherein X and X1 ea h p esent amernher se ecte .from theoup co t g at a hyd ge a m a hlo in atom nd a lower alky g oup havin atmos 3 ca b n a om and Y and 1 ea h r prese ts a mem er se ecte m e groupisti g of a hyd og n atom, a owe a kyl group avi g at m s 3 ca bon atms, a lo e monoydroxy al y up having t m st 3 ca bon atoms, slow y yalkyl group ng a m t 3 arbon at ms and a benzyl radical.

11. A process for theoptical brightening of polyacry lor nitrile fiberswhich comprises applying to said fibers in aqueous medium from 70.01 to3.0 percent, calculated on the weight of said fibers, of the opticalbrightening agent of the formula 12. A process for the opticalbrightening of polyacrylonitrile fibers which comprises .applying tosaid fibers in aqueous medium in a finely dispersed state from 0.01 to3.0 percent, calculated on the weight of said fibers, of the opticalbrightening agent of the formula 13. A process for the opticalbrightening of polyacrylonitrile fibers which comprises applying to saidfibers in aqueous medium in the presence .9; a dispersing agent 12 from0.01 to 3.0 percent, calculated onthe Weight of said fibers, of theoptical brightening agent of the formula 14. A process for the opticalbrightening of polyacrylopitrile fibers which comprises applying to saidfibers in aqueous medium in the presence of a washing agent from 0.01 to3.0 percent, calculated on the weight of said fibers, of the opticalbrightening agent of the formula 15 A composition of mattersubstantially consisting of polyacrylonitrile fibers having incorporatedtherein an optical brightening agent in a proportion sufiicient tobrighten said fibers, said optical brightening agent being of theformula 16. A process for the optical brightening of polyacrylo- 1nitrile fibers which comprises applying to said fibers in and a compoundof'the formula w e n X d 1 ea rep esents a member selec fromthe groupconsisting of a hydrogen atom, a chlorine atom and a lower alkyl grouphaving at most 3 carbon atoms and Y and Y each represents a memberselected from the group consisting of a hydrogen atom, a lower alkylgroup having at most 3 carbon atoms, a lower alkenyl group having atmost3 carbon atoms, a lower mqnohydroxy alkyl group having at most 3 carbonatoms a lower di-hydrogry alkyl group having at most 3 carbon atoms anda benzyl radical.

17. A composition of matter substantially consisting ofpolyacrylonitrile fibers having incorporated therein an opticalbrightening agent in a proportion sufiicient to brighten said fibers,said optical brightening agent being selected from the group consistingof the compound of the formula and a compound of the formula wherein Xand X each represents a member selected from the group consisting of ahydrogen atom, a chlorine atom and a lower alkyl group having at most 3carbon atoms and Y and Y each represents a member selected from thegroup consisting of a hydrogen atom, a lower alkyl group having at most3 carbon atoms, a lower alkenyl group having at most 3 carbon atoms, alower mono-hydroxy alkyl group having at most 3 carbon atoms, a lowerdi-hydroxy alkyl group having at most 3 carbon atoms and a benzylradical.

References Cited in the file of this patent UNITED STATES PATENTS2,463,264 Graenacher et a1. Mar. 1, 1949 5 2,488,094 Graenacher et a1.Nov. 15, 1949 2,604,454 Ackermann July 22, 1952 2,773,869 Leavitt Dec.11, 1956 2,838,504 Crounse June 10, 1958 2,875,089 Ackermann Feb. 24,1959 OTHER REFERENCES Dorman et al.: Relationship Between Structure ofDyes and Their Dyeing Characteristics on Hydrophobic 15 Fibers, AmericanDyestufl Reporter, July 5, 1954; pages Patent No, 3,005, 779 October24,, *19-61 Franz Ackermann et a1.

It is hereby certified that er ent requiring correction and that tcorrected below.

ror appears in the above numbered pathe said Letters Patent should readas Column 4, line 8, for "preparation?" 12, formula (5) t as shown belowin after "use" insert one line 23, read preparations column 5, lines 6to he center portion of the formula should appear stead of as in thepatent:

' HC CH I I Signed and sealed this 15th day of May 1962.

(SEAL) Attest: ERNEST W, SWIDER Commissioner of Patents

16. A PROCESS FOR THE OPTICAL BRIGHTENING OF POLYACRYLONITRILE FIBERSWHICH COMPRISES APPLYING TO SAID FIBERS IN AQUEOUS MEDIUM FROM 0.01 TO3.0 PERCENT, CALCULATED ON THE WEIGHT OF SAID FIBERS, OF A MEMBERSELECTED FROM THE GROUP CONSISTING OF THE COMPOUND OF THE FORMULA